The present invention relates to a structural enhancer for beams of lumber, and more particularly to such an enhancer which provides a high moment of inertia of the beam/enhancer composite with only a modest increase in weight over the beam itself.
In instances where a beam of wood will be subject to severe torsional forces (that is, transverse or other non-axially directed forces), it is known to reenforce the beam by securing to it an axially extending flitch plate formed of structural metal. The flitch plate may be in configuration a planar plate, a right-angle brace (where only torsion of a given moment is expected), or a C- or U-shaped member wherein the web or bight extends along one side of the beam, with each of the legs being bent generally transverse to the web to extend along a respective one of the opposing sides of the beam. The conventional planar flitch plate has a different thickness than the beam, but preferably shares the axial and transverse dimensions thereof.
The conventional planar flitch platexe2x80x94and indeed to some degree the right-angle, and U or C flitch platesxe2x80x94is not entirely satisfactory for its intended use. This is because in the composite the increase in the moment of inertia produced by the flitch plate (relative to the moment of inertia of the beam alone) is purchased at the expense of a substantial increase in weight of the composite (relative to the weight of the beam alone), even when the transverse dimension of the U or C plate is less than that of the beam.
Additionally, the flitch plate is typically custom fabricated, therefore requiring shop drawings and the fabrication time required by a steel shop to make the flitch plate. Assembly of the composite (that is, the flitch plate and the beam) is commonly performed using a torch and bolts, a time-consuming process not well suited to field installation.
Accordingly, it is an object of the present invention to provide an enhancer which replaces a conventional flitch plate, whether planar, right-angled, or C or U shaped.
Another object is to provide such an enhancer composite having about the same moment of inertia (or even higher) as a comparable conventional flitch plate composite.
A further object is to provide such enhancer composite being about as light (or even lighter) than a comparable conventional flitch plate component.
It is an object of the present invention to provide such enhancers which would be available at lumberyards in various sizes to fit standard dimensional lumber, with the wall thickness of the enhancer web being available in standard gauges.
It is another object to provide a composite of the enhancer and a beam of wood.
It has now been found that the above and related objects of the present invention are obtained in a lumber structural enhancer of unitary, one-piece and integral construction adapted for use with an axially extending beam of wood, the beam being of substantially rectangular cross-section and having a pair of opposing sides and at least one bight connecting the opposing sides. The enhancer comprises an axially extending, thin, substantially planar web of structural metal, and a pair of axially extending folded tubes of structural metal, the tubes being of substantially rectangular cross-section and connected by the web. The web is configured and dimensioned to overlap and abut the beam bight, and each of the tubes is configured and dimensioned to overlap and abut a respective one of the pair of opposing beam sides.
The tubes may be transversely aligned and extend to the same side of the web or not transversely aligned and extend to respective opposite sides of the web. The tubes are preferably four linear segment tubes folded from a single piece of structural metal, the first and last segments at least closely approaching each other in substantially transverse relationship. The tubes are optimally five linear segment tubes folded from a single piece of structural metal, the first and last segments overlapping and at least partially abutting each other in substantially parallel relationship.
The present invention additionally encompasses in combination at least one such axially extending beam of wood, and an enhancer secured thereto.